Answer :
Final answer:
To calculate the formal charge of nitrogen in ammonia (NH3), one subtracts the number of non-bonding electrons and half of the bonding electrons from the total number of valence electrons. Nitrogen has a formal charge of 0, as do each of the hydrogen atoms, leading to a net charge of 0 for the molecule.
Explanation:
Calculating Formal Charge
To calculate the formal charge on an atom within a molecule or ion, you use the formula:
Formal Charge = (Valence electrons) - (Non-bonding electrons) -
(
1/2
* Bonding electrons)
For ammonia (NH3), the Lewis structure indicates one lone pair (2 electrons) and three bonding pairs (6 electrons shared with hydrogen atoms) for the nitrogen atom. The calculation for nitrogen's formal charge would be:
Formal Charge of N = (5 valence e-) - (2 lone pair e-) - (
1/2
* 6 bond pair e-) = 0
Every hydrogen atom in ammonia has one bond with nitrogen, and no non-bonding electrons. Therefore, each hydrogen has a formal charge of:
Formal Charge of H = (1 valence e-) - (0 lone pair e-) - (
1/2
* 2 bond pair e-) = 0
The sum of the formal charges in ammonia is thus 0 for each hydrogen and 0 for the nitrogen, giving a net charge of 0 for the molecule.
The formal charge should not be confused with the oxidation state, which is a different concept used primarily for tracking electrons in redox reactions. While formal charges must add up to the net charge on the molecule or ion, oxidation states do not necessarily correlate with the actual charge distribution.
